fix: limit email subject length

Add limitation for subject length (128 chars) and the
corresponding help text.

src/components/bulk-email-tool/bulk-email-form/BulkEmailForm.jsx

@@ -281,7 +281,10 @@ function BulkEmailForm(props) {
         />
         <Form.Group controlId="emailSubject">
           <Form.Label className="h3 text-primary-500">{intl.formatMessage(messages.bulkEmailSubjectLabel)}</Form.Label>
-          <Form.Control name="emailSubject" className="w-lg-50" onChange={onFormChange} value={editor.emailSubject} />
+          <Form.Control name="emailSubject" className="w-lg-50" onChange={onFormChange} value={editor.emailSubject} maxLength={128} />
+          <Form.Control.Feedback className="px-3" type="default">
+            {intl.formatMessage(messages.bulkEmailFormSubjectTip)}
+          </Form.Control.Feedback>
           {!emailFormValidation.subject && (
             <Form.Control.Feedback className="px-3" hasIcon type="invalid">
               {intl.formatMessage(messages.bulkEmailFormSubjectError)}

src/components/bulk-email-tool/bulk-email-form/messages.js

@@ -41,6 +41,11 @@ const messages = defineMessages({
     defaultMessage: 'Subject',
     description: 'Email subject line input label. Meant to have colon or equivilant punctuation.',
   },
+  bulkEmailFormSubjectTip: {
+    id: 'bulk.email.form.subject.tip',
+    defaultMessage: '(Maximum 128 characters)',
+    description: 'Default Subject tip',
+  },
   bulkEmailFormSubjectError: {
     id: 'bulk.email.form.subject.error',
     defaultMessage: 'A subject is required',